Health and socio-demographic characteristics associated with uptake of seasonal influenza vaccination amongst pregnant women: retrospective cohort study

Pregnant women are at increased risk from influenza, yet maternal influenza vaccination levels remain suboptimal. This study aimed to estimate associations between socio-demographic and health characteristics and seasonal influenza vaccination uptake among pregnant women and understand trends over time to inform interventions to improve vaccine coverage. A retrospective cohort study using linked electronic health records of women in North West London with at least one pregnancy overlapping with an influenza season between September 2010 and February 2020. We used a multivariable mixed-effects logistic regression model to identify associations between characteristics of interest and primary outcome of influenza vaccination. 451,954 pregnancies, among 260,744 women, were included. In 85,376 (18.9%) pregnancies women were vaccinated against seasonal influenza. Uptake increased from 8.4% in 2010/11 to 26.3% in 2018/19, dropping again to 21.1% in 2019/20. Uptake was lowest among women: aged 15-19 years (12%) or over 40 years (15%; OR 1.17, 95% CI 1.10 to 1.24); of Black ethnicity (14.1%; OR 0.55, 95% CI 0.53 to 0.57), or unknown ethnicity (9.9%; OR 0.42, 95% CI 0.39 to 0.46), lived in more deprived areas (OR least vs most deprived 1.16, 95% CI 1.11 to 1.21), or with no known risk factors for severe influenza. Seasonal influenza vaccine uptake in pregnant women increased in the past decade, prior to the COVID-19 pandemic, but remained suboptimal. We recommend approaches to reducing health inequalities should focus on women of Black ethnicity, younger and older women, and women living in areas of greater socio-economic deprivation